FIG. 1 is a schematic diagram illustrating an amplifying module 100 for related art. As shown in FIG. 1, the amplifying module 100 comprises PGAs (programmable gain amplifier) A1-A5 coupled in series. An input signal INS transmitted to the programmable gain amplifier A1 will be amplified by all programmable gain amplifiers A1-A5 to generate an output signal OS.
Each programmable gain amplifier has a limit for its input/output swing. However, since the swing of each stage but the last (A5) in the programmable gain amplifier cannot be easily acquired (ex. A1-A4), the intermediate signal swing in such programmable gain amplifiers may saturate if all stages' amplifying gains thereof are not well controlled.
Additionally, the amplifying gains may drift due to PVT (process, voltage, temperature) variation, thus a good mechanism for acquiring or tuning amplifying gains is desired.